Stock Market Analytics Zoomcamp - Module 3

Change bytes into char inside data type of VARCHAR2  

begin
for r in
    (select owner, table_name, column_name, data_length
      from all_tab_columns
      where data_type = 'VARCHAR2' 
      and char_used = 'B' and owner = 'SCHEMA')
loop
execute immediate 'alter table ' || r.owner || '.' || r.table_name
|| ' modify ' 
|| r.column_name 
|| ' varchar2('
|| r.data_length
|| ' char)';
end loop;
end;
/

Note: Replace SCHEMA with owner of the tables